In data networks having a plurality of data network nodes, a data connection takes place from a source to a destination via a route, link, or path, in the data network which includes a certain number of data network nodes. In an end-to-end connection in such a data network, therefore, data packets run from the source to the destination via a plurality of data network nodes. These data network nodes work like relay stations.
In a data network having dynamic or mobile data network nodes, for example, a radio communications network having mobile radio terminals as data network nodes, the transmission quality of a data connection fluctuates as a rule. Such data networks are expected to gain increasing importance in the future, for example, because of the wide distribution of wireless LAN networks occurring in the meantime, and the introduction of UMTS (universal mobile telecommunications system). Therefore, when working with such data networks one desires to achieve a high data transmission rate, in spite of the fluctuating transmission quality.
In radio communications networks, a distinction is made between subscriber networks and ad hoc networks. Ad hoc networks permit a self-organizing organization. Since, the radio range in radio systems having a high data rate is limited, so-called multihop data connections are increasingly used in data networks. For example, in an ad hoc radio communications network, individual laptop computers may be used as data network nodes which are provided with a radio interface operated in ad hoc mode. Multihop data connections are used, above all, when the destination is not located in the direct radio range of the source. The connection setup, the connection finding and the restoration of connections are ensured by special routing protocols.
As soon as a data connection between a source and a destination has been found and set up, it may be used for data transport. Depending on the dynamics of the data network nodes participating in the data connection, the quality of the data connection may now change continuously. The data connection may be interrupted if a data network node participating in the data connection moves out of the radio range of its adjacent data network node. In such a case, a data network node adjacent to the breaking point informs the source about the breaking point in the data connection. The source then tries again to set up a new connection to the destination. To do this, the source initiates the renewed transmission of a so-called connection search message, which is sent through the entire data network. In this case, one speaks of “flooding” the data network, since the connection search message “floods” the entire data network. This “flooding” is a high requirement for network capacity. In addition, the network capacity required for the “flooding” is not available to other network connections.
Moreover, upon breaking a data connection, no data transport is possible any longer between source and destination. Data packets which were already sent from the source to the destination, but which could not pass the breaking point in time, are lost. Thus, such data packets must be sent again by the source to the destination, resulting in an increase in packet delay as well as a waste of capacity in packet-oriented data networks. In transport protocols, such as TCP (transport control protocol) used on the Internet, these great delays lower the throughput of a data connection, and therewith of the entire data network.
In order to achieve an especially high quality in a data connection, one desires the continuity of an end-to-end connection. This applies if commercial services are to be offered over such data networks.